Some C compiler flags may be added by default depending on your
environment. Specify optflags=.. and warnflags=.. as necessary to override
them.

vendor_ruby directory

A new library directory named `vendor_ruby' is introduced in addition
to `site_ruby'. The idea is to separate libraries installed by the
package system (`vendor') from manually (`site') installed
libraries preventing the former from getting overwritten by the latter,
while preserving the user option to override vendor libraries with site
libraries. (`site_ruby' takes precedence over `vendor_ruby')

If you are a package maintainer, make each library package configure the
library passing the `–vendor' option to `extconf.rb' so that the
library files will get installed under `vendor_ruby'.

You can change the directory locations using configure options such as
`–with-sitedir=DIR' and `–with-vendordir=DIR'.

String#slice! had some
unintentional bugs and they have been fixed because either they disagreed
with documentation or their respective behavior of slice. Unfortunately,
this causes some incompatibilities in the following (somewhat rare) cases.

slice! no longer expands the array when an out-of-boundary value is given.

Time#to_date and Time#to_datetime are added as
private methods. They cause name conflict error in ActiveSupport 1.4.1 and
prior, which comes with Rails 1.2.2 and prior. Updating ActiveSupport
and/or Rails to the latest versions fixes the problem.

digest

The constructor does no longer take an initial string to feed. The
following examples show how to migrate: